I have never frostseeded. I drilled mine in the summer time after I killed everything off and reduced everything to bare dirt. This was July 2013
This is June 2014. Lots of giant ragweed came in as well, which is fine and didn't hurt anything.
Here is a detail of the switch itself in July of 2014. The yellow stick is 48" long.
Once you have it and it can get established it's pretty tough stuff. I had loggers run over some of mine this past summer and what got matted down turned brown and died. I was worried.....I shouldn't have been. It has already generated new grass - shorted due to reduced growing season, but it's fine and will bounce back next summer just fine.
I use mine for buffers - I have seen where deer like the edges between the grass and my timber - but I have not seen much use of smaller "chunks" of the switch for bedding. It also seems to stand fairly well in the winter so that's a plus.
You mention a road screen - how tall do you need? I'm right at 6 feet tall and I can easily see across my switch - it will hide deer, but it won't hide me.
The screening comes from the grass and not the seed heads. I would only anticipate getting about 4 or 5 feet of actual screening height - at least from what I have seen. This is Summer 2015 - that is my 790JD tractor. I am standing outside this buffer on a mowed path and the trees in the back are roughly 120 feet away. As you can see - it will hide a deer with no issues, but you don't have a wall at eye level.